Bobcat 743 skidsteer

Does anyone here have a experience with these. It has a little 4cyl na engine made by kubota. I recently purchased it . It has a few issues. No one being that it overheats. It starts and runs but it over pressure the coolant system causing it to blow our the cap on the coolant reservoir. Rad is good and clean. No oil in coolant or coolant in oil. Previous owner thinks it is a head gasket problem but there are no external leaks.im thinking maybe a thermostat or waterpump problem. Idk. Any advice .

I've not had any experience with the 4cyl Kubota diesels, but in my IH Cub Cadet hobby, there were a few 3 cyl Kubota Diesel and Gas engines put in a few models of Cub's. I would start with the thermostat water pump...... KUBOTA ONLY (take your Vaseline with you). These can have thermostat issues. However, pressurizing the the cooling system does worry me. We had a guy with this same type of issue, and found it was a head gasket. Hopefully not, and I don't remember him mentioning mixing of fluids, would just get hot and spew......... They are nice little engines, one day I want a rattly Cub Cadet.......